fwht: Fast Walsh-Hadamard Transform

In gsignal: Signal Processing

Fast Walsh-Hadamard Transform

Description

Compute the (inverse) Fast Walsh-Hadamard transform of a signal.

Usage

ifwht(x, n = NROW(x), ordering = c("sequency", "hadamard", "dyadic"))

fwht(x, n = NROW(x), ordering = c("sequency", "hadamard", "dyadic"))

Arguments

x	input data, specified as a numeric vector or matrix. In case of a vector it represents a single signal; in case of a matrix each column is a signal. fwht operates only on signals with length equal to a power of 2. If the length of x is less than a power of 2, its length is padded with zeros to the next greater power of two before processing.
n	transform length, specified as a positive integer scalar. Default: NROW(x).
ordering	order of the Walsh-Hadamard transform coefficients, one of: "sequency" (Default) Coefficients in order of increasing sequency value, where each row has an additional zero crossing. "hadamard" Coefficients in normal Hadamard order "dyadic" Coefficients in Gray code order, where a single bit change occurs from one coefficient to the next

Value

(Inverse) Fast Walsh Hadamard transform, returned as a vector or matrix.

Author(s)

Mike Miller.
Conversion to R by Geert van Boxtel, [e-mail].

References

https://en.wikipedia.org/wiki/Hadamard_transform

https://en.wikipedia.org/wiki/Fast_Walsh-Hadamard_transform

Examples

x <- c(19, -1, 11, -9, -7, 13, -15, 5)
X <- fwht(x)
all.equal(x, ifwht(X))

gsignal documentation built on Sept. 12, 2024, 6:27 a.m.